# Calculate The Dot Product of A = (−4,−9) and B = (−1,2)

Calculate the dot product of a = (−4,−9) and b = (−1,2) . What type of angle the vectors will form?

SOLUTION:

Using the following formula for the dot product of two-dimensional vectors,

ab = a1b1+a2b2,

we calculate the dot product to be

ab = a1b1+a2b2

ab = -4(-1) – 9(2)

ab = 4 - 18

ab = -14.

Since
ab is negative, we can infer that the vectors form an obtuse angle